The basis of the priority right of the present application is Japanese Patent Application No. 2000-194929 (filing date: Jun. 23, 2000), and the contents of the above-mentioned Japanese application are deemed to be incorporated in the present specification.
1. Field of the Invention
The present invention relates to pipelines for running cryogenic (very-low-temperature) liquid such as liquid oxygen, liquid hydrogen and the like which is used for rocket fuel and relates more particularly to a device for coupling and separating coupling (jointer) units of the pipelines.
2. Description of the Related Art
A bayonet coupling (jointer) by which coupling and separation can be easily and reliably carried out has been often adopted for the pipelines in which cryogenic liquid f lows. However, when this bayonet coupling is used, the inside bayonet couplings are coupled to or separated from each other, in order to keep the insides of the pipelines clean, after surroundings of the coupling units are covered with vinyl or plastic or the like, or after a ball valve is installed and the valve is opened or closed.
In other words, if the insides of the pipelines are exposed to the open air when the coupling or the separation of the bayonet coupling units is performed, dust and moisture in the air can intrude into the insides of the pipelines. As a result, the insides of the pipelines are polluted or the condensation of the moisture is left in the insides of the pipelines, and this can cause the deterioration of the purity of the cryogenic liquid. Accordingly, a method to prevent the pollution when the coupling or the separation is carried out and to keep the purity as high as possible is adopted. Specifically, when liquid flowing in the pipelines is cryogenic liquid which is used for rocket fuel such as liquid oxygen, liquid hydrogen or the like, it is required that the degree of the purity be kept to be in an extremely high level, in order to keep the insides of the pipelines clean.
By the way, in a method by which the surroundings of the coupling units are covered with vinyl or plastic in order to maintain the purity of the insides of the pipelines, it is impossible to promptly carry out the coupling or the separation of the coupling units, because every time the operation of coupling or separation is carried out it is necessary to put on and take off vinyl or plastic. Moreover, in this method it is extremely difficult to completely prevent the contamination, because when the separation is carried out the insides of the pipelines are exposed to the outside for a moment.
On the other hand, in another method by which a ball valve or the like is installed around the coupling units, there is also fear that the purity of the insides of the pipelines deteriorates by the intrusion of dust and by a dew-point rise, because the insides contact with the outside air even though the insides contact with the outside air only for a minute when the ball valve is opened and closed.
There is another technique (see Japanese Patent Application, Laid Open Publication No. 64-40786), wherein the surroundings of the coupling units are covered with a box and then helium gas is provided into the box and thereby freezing of the coupling units is prevented when cryogenic oxygen or the like is poured or discharged. However, even by this technique, when the coupling units are separated from each other, it is impossible to avoid the inside pollution because the insides of the pipelines become open to the outside momentarily.
Therefore, conventionally after coupling or separation, the insides of the pipelines have been purged by using clean nitrogen gas having prescribed purity and a prescribed dew point. Thereby, the purity of the pipelines becomes higher and a dew point drops. However, it takes a considerable time to depress a dew point to a prescribed value and also it takes a certain time to carry out the purity analysis and the dew point analysis as well. Therefore, it has been difficult to carry out the quick coupling and the quick separation of the coupling units.
It is one object of the present invention to provide a device for coupling pipelines in which cryogenic liquid flows, wherein both coupling units are reliably separated from and coupled to each other without polluting the insides of the pipelines by the inflow of dust or moisture in the open air and with the inside kept highly clean.
It is another object of the present invention to provide a device for coupling pipelines in which cryogenic liquid flows, wherein both coupling units can be promptly coupled to and separated from each other.
It is another object of the present invention to provide a device for coupling pipelines in which cryogenic liquid flows, wherein positioning the pipelines (align the axes of the pipelines with each other) can be easily and reliably carried out when coupling is performed.
In order to achieve these purposes, the present invention provides a coupling device, wherein one of the coupling units is confronted with the other of the coupling units for carrying out separation and coupling, and wherein this coupling device comprises: a pair of flanges which are pierced by the coupling units to support the coupling units with the coupling units moving close to or away from each other at will and which form compartments (i.e., rooms which can be isolated from the open air) around the coupling units; a pair of inner cover units which open or close the surfaces at the ends of the coupling units; a pair of outer cover units which open or shut the compartments of both flanges; and purge lines which purge the insides of the compartments.
That is, in the present invention, firstly the inner cover units which open or close the coupling units are provided on this device. When separation is carried out, it is possible to cut off contact with the outside air by shutting the insides of the pipelines with the inner cover units. Therefore, the pollution in the pipelines by the inflow of dust and moisture can be prevented. Secondly, the flanges which support the coupling units with the coupling units freely approaching and separating from each other are installed on both coupling units, and the compartments of the flanges are opened and closed by the outer cover units. Thereby, it is possible to isolate the compartments of the flanges from the outside air. Thirdly, the purge lines are provided on the flanges having these compartments. Thereby, the insides of the compartments can be purged by using clean purge gas. It is thus possible to joint and separate both coupling units without the pollution by the inflow of dust or moisture from the open air when the inner cover units are opened.
As a result, it becomes possible to securely carry out the separation and the coupling of the coupling units with the insides of the coupling units kept highly pure. Moreover, it becomes possible to take less time to depress a dew point (the dew-point depression is carried out after separation and connection) and it becomes unnecessary to carry out the dew-point analysis as well as the purity analysis. Accordingly, it becomes possible to perform quick connection and quick separation.
Furthermore, one of the flanges is made to have insertion pins for positioning and the other of the flanges is made to have insertion holes into which the insertion pins are inserted. By using the insertion pins and the insertion holes, positioning the pipelines (aligning the axes of the pipelines) can be easily and reliably carried out particularly when coupling is carried out.